In a continuation of our study into the structure and function of the opiate receptor system, the first enantiomeric pair of alkylating opiates have been prepared. These enantiomers have been shown to exhibit substantial stereoselectivity for the delta opiate receptor from NG108-15 cells. The highest affinity enantiomer has been utilized for purification of the delta, opiate receptor from NG-108-15 cells to apparent homogeneity.